The files in this package can be unpacked in the PROJ data directory. For an installed PROJ this may be /usr/local/share/proj or /usr/share/proj on unix style operating systems.
About the World PROJ resource package
The World PROJ resource package is a collections of grids that are too large to be in the general purpose proj-datumgrid package and not essential for the functionality of PROJ, but still of general interest to PROJ-users.
Vertical grid: EGM2008 geoid model
Format: GTX License: Public Domain
2.5 minute worldwide geoid undulation grid that transforms physical heights to WGS84 ellipsoidal heights.